*,
*::before,
*::after {
    box-sizing: border-box;
}

body {
    position: relative;
    background-color: #eee;
    min-height: 1000px;
    margin: 0;
    padding: 0;
}

#app {
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    width: 200px;
    height: 200px;
    border: 1px dashed black;
}
